Table 4.

Descriptions of parent and child outcomes: MBRS responsivity and directiveness items (Mahoney et al., 1998), engagement states (Adamson et al., 2009) and CBRS items (Mahoney & Perales, 2003).

	Description
MBRS item
Responsivity (κ = 0.87)	A parent’s active and appropriate response to the child’s actions on objects as well as both verbal (e.g. vocalizations, language) and non-verbal communication and behaviour (e.g. gestures, body language, facial expression). Coding anchors: 1 = ‘highly unresponsive’ parent chronically fails to respond to the child’s behaviours. 3 = ‘consistently responsive’ parent who may at times be slow or inappropriate but is otherwise responsive. 5 = ‘highly responsive’ parent that responds immediately and appropriately to both overt and subtle child behaviours.
Directiveness (κ = 0.80)	A parent’s non-verbal and verbal prompting including requests, question asking and commands that directs or controls the child’s behaviour. Coding anchors: 1 = ‘very low directive’ parent who allows the child to initiate and play without interfering, withholds suggestions until requested. 3 = ‘moderately directive’ parent who about half the time allows child to initiate, may direct how the child should play or what to play. 5 = ‘extremely directive’ parent who continually redirects the child, extreme frequency of commands, training, requests and instruction where the parent completely control the interaction.
Engagement
Unengaged (α = 0.99)	Child is not engaged with any object or person. For example, the child may be scanning the environment, wandering or engaging in self-stimulatory motor behaviours.
Object (α = 0.99)	Child is exclusively engaged with an object to the exclusion of the parent (e.g. the child is actively operating a pop-up toy alone or building with blocks without any participation by the adult).
Supported joint (α = 0.97)	Child and parent are actively engaged in a shared referent. The child is aware of the parent’s participation (e.g. notices parent’s actions on object and child joins in the play; child and parent are actively taking turns on an object) but does not repeatedly and overtly acknowledge the parents’ participation via eye contact.
Supported joint with symbols (α = 0.82)	Child and parent are actively engaged in a shared referent and the child demonstrates an awareness of the parent’s participation. Additionally, the child acknowledges the parent’s use of symbols (e.g. child follows parent suggestion about how to act on an object) or the child uses symbols in reference to the shared activity (e.g. child and parent are rolling a ball back and forth and the child talks about the activity (e.g. ‘roll ball’) without making eye contact with the parent).
Coordinated joint (α = 0.99)	Child actively and repeatedly acknowledges both the shared activity and the interaction partner through eye contact and gestures (e.g. pointing, showing or giving objects).
Coordinated joint with symbols (α = 0.98)	Child actively and repeatedly acknowledges both the shared activity and the interaction partner through eye contact and gestures (e.g. pointing, showing or giving objects). Additionally, the child responds to or uses language in reference to the shared activity.
Social behaviour
Affect (κ = 0.93)	Describes the child’s emotional state (distress vs enjoyment) during the interaction indicated by frequency of smiling, laughing or vocalizing directed towards the parent. Coding anchors: 1 = ‘Very low’ – child demonstrates distress evidence through crying, whining or aggressive behaviours. 3 = ‘Moderate’ – child is neutral displaying little overt enjoyment. 5 = ‘Very high’ – child shows enjoyment through laughing, smiling and vocalizations when interacting with the parents and the activities. No demonstration of negative affect.
Attention (κ = 0.73)	Degree to which child is active, attentive and engaged in activities. Children who frequently change activities (flitting) or have sustained period of inattention will score lower on this item. Coding anchors: 1 = ‘Very low’ – inactive, avoidance and rarely ever attend to activity. 3 = ‘Moderate’ – attends about 50% of time. 5 = ‘Very high’ – child sticks with activity throughout session without periods of inattention.
Cooperation (κ = 0.87)	Degree to which a child complies with adult demands, requests and suggestions rather than rejecting or refusing. Coding anchors: 1 = ‘Very low’ – child may throw or otherwise reject objects or ignore the parent’s activity suggestions. 3 = ‘Moderate’ – 50% of the time the child cooperates with adult requests or suggestions 5 = ‘Very high’ – child cooperates consistently throughout the sessions, responding quickly to both overt and subtle suggestions.
Interest (κ = 0.93)	Represents child’s motivation and satisfaction in the activities that he/she engages in throughout the interaction. Coding anchors: 1 = ‘Very low’ – child obviously does not obtain satisfaction from the activity; may be highly distracted with neural affect. 3 = ‘Moderate’ – some satisfaction in activities, sustained periods using non-verbal or verbal communication to show satisfaction. 5 = ‘Very high’ – highly involved throughout the session with the activity, showing satisfaction in the activity where the activity can be either child- or parent initiated.
Joint attention (κ = 0.94)	Frequency with which a child uses eye contact with the parent, directs vocalizations coordinated with eye contact to the parent or uses a joint attention gesture (point, show or give object). Coding anchors: 1 = ‘Very low’ – no eye contact, non-verbal gestures or verbal attempts to share with the parent. 3 = ‘Moderate’ – child show periods of eye contact, periods may be in response to adult’s bids rather than initiated by the child. 5 = ‘Very high’ – child initiates sharing through eye contact, gestures and/or language frequently and for sustained periods of time. The child frequently tries to involve the adult.
Persistence (κ = 0.87)	Frequency with which a child independently repeats or practises a behaviour when they encounter difficulty. Coding anchors: 1 = ‘Very low’ – never demonstrates repetition or second attempt at activity when having difficulty. 3 = ‘Moderate’ – extended periods where child appears to be practising behaviour, just as often as when he/she does not practise. 5 = ‘Very high’ – frequently practises vocalizations or activities as well as repeated attempts at tasks when having difficulty.